1. Field of the Invention
The present invention relates generally to scene imaging systems (SIS's) and more particularly to an SIS for providing an enhanced image with embedded symbology.
2. Description of the Related Art
Many devices, such as aircraft, are typically designed to provide a real-world view of the out-the-window scene for at least one operator to operate the device. In the past, a view of the scenery outside the device was provided through passive means, such as a cockpit windshield, or artificial means through sensors and displays.
Scene imaging systems such as Enhanced Vision Systems (EVS) supplement out-the-window vision via the use of camera/sensor imagery superimposed over the real-world view. EVS include sensors that can detect and display images of objects that pilots would not normally be able to see when looking through the cockpit window of an aircraft. For example, EVS can present data from sensors that can penetrate low-visibility weather conditions and darkness, such as radar or forward-looking infrared (FLIR). The data presented from the sensors is derived from the current environment and not from a computer database. EVS can be used on both head-down and head-up displays. Other features such as navigation enhancements and proactive systems to avoid controlled flight into terrain and runway incursions can also be integrated in EVS.
To achieve lower minima landing credit using an Infrared (IR) based EVS system, the integrity of both the IR sensor and display device (e.g., a Head Up Guidance System) must meet minimal integrity requirements based on the function being performed. To meet these integrity requirements the system must have a method to detect the display of frozen, flipped or misaligned EVS images.
In response to these problems, U.S. Pat. No. 7,355,179, issued to R. B. Wood et al., entitled “Scene Imaging System Integrity Monitor and Method Thereof”, discloses a scene imaging system (SIS) integrity monitor for monitoring the required operation of an imaging sensor of an SIS. The SIS is of a type including: i) an imaging sensor, ii) an imaging system processor, and iii) an imaging system display. The SIS integrity monitor includes a signal emitter assembly for receiving emitter drive signals from an imaging system processor and directing a monitoring image into the active field of view of an imaging sensor for sensed image generation. The generated image is provided to the imaging system processor for analysis. The imaging system processor evaluates the location and modulation state of the generated image to determine if faults exist in the image generation or image display paths.
U.S. Pat. Pub. No. 20020088951, by J. C. Chen, entitled “Method and Apparatus for Detecting Aberrations in an Optical System” discloses a method of detecting aberrations associated with a projection lens utilized in an optical lithography system. Chen discloses doing a ‘static’ optical quality test during manufacture. It does not involve doing a real time, continuous ‘monitor’ of the entire imaging system; specifically detecting run-time errors in the system (i.e. random failures in the camera that could lead to a misleading display of information such as the video from the camera freezing).
U.S. Pat. No. 7,355,179, issued to J. R. Kerr, entitled “Enhanced Vision System Sensitive to Infrared Radiation”, discloses an enhanced vision system and method for use with vision systems with an imager sensitive to infrared radiation of less than 2-microns in wavelength, to produce a first image signal. Another imager sensitive to infrared radiation at least 3-microns in wavelength may be used to produce a second image signal. Preferably, the first image signal represents sensed electric light sources, and the second image signal represents sensed background such as terrain, runways, structures, and obstacles. A signal processor combines an image signal representing locally maximum values of the first image signal with the second image signal to create a displayed image. As in the Chen system, the Kerr system does not involve doing a real time, continuous ‘monitor’ of the entire imaging system. Kerr only covers the use of multiple IR cameras to generate a single, merged, video display. As will be disclosed below, present applicant's invention, on the other hand, monitors the real-time integrity of such a system.